Carriage reciprocator and positioner with continuously moving chain

ABSTRACT

A carriage reciprocator and positioner is provided with two air clutches and a continuously moving chain. The chain is arranged to move over co-planar spaced sprockets so as to present one direction of chain motion to the top of the carriage and a second direction of chain motion to the bottom of the carriage. The carriage is also provided with two chain engaging sprockets each controlled by a respective one of two air clutches. The chain engaging sprockets on the carriage normally idle with chain motion. However actuation of the controlling air clutch halts the spinning and forces the sprocket and clutch to act as a unit to thereby move the carriage linearly along the length of the chain in a direction dependent upon which portion of the chain was so engaged. Means are provided to automatically reverse the stroke, to vary the length of the stroke and to vary the speed of the stroke.

BACKGROUND OF THE INVENTION

This invention is directed to a carriage reciprocator and positioner.This invention is related to a class of devices known as chainreciprocators.

Present day chain reciprocators have carriages connected directly to achain. Reciprocation of the carriage is achieved by reversing the motionof the chain. Reversal of chain motion can have detrimental effectsespecially in those applications where high speed, short stroke carriagereciprocation is required. In such applications and others the chainlife is shortened since the chain is required to take most of theinertial shock of carriage reversal. In addition, in high speed, shortstroke reciprocation environments, one section of the chain tends towear excessively which usually leads to differential wear of thesprocket teeth and resultant chain slap.

SUMMARY OF THE INVENTION

Accordingly, it is an object of this invention to provide a carriagereciprocator and positioner having a chain which continuously runs inone direction and wherein most of the inertial shock of carriagereversal is absorbed by the carriage. It is a further object of thisinvention to provide a device wherein all of the chain is used, whereindevice longevity and reliability are increased, wherein the velocity ofthe carriage is controllable, wherein chain life is extended and whereina unique arrangement of air clutches, chain sprockets and associatedelements, are arranged to automatically achieve carriage reciprocationalong an adjustable stroke length. These and other objects of theinvention are achieved as follows.

A carriage is provided with two air clutches each of which controls arespective one of two carriage mounted chain sprockets. The carriage isarranged to move along two vertically spaced co-planar rails which areeach separately attached to a housing. The housing supports a variablespeed motor which is arranged to continuously drive an elongated rollerchain around two spaced co-planar sprockets. The chain lies in a planewhich is parallel to and situated between the carriage plane and theplane of the rails.

The continuously running roller chain presents one direction of chainmotion to the top of the carriage and an opposite direction of chainmotion to the bottom of the carriage. One of the carriage mountedsprockets engages the chain near the top of the carriage and the othercarriage mounted sprocket engages the chain near the bottom of thecarriage. Each of the carriage mounted sprockets is arranged to normallyidle with chain motion and the carriage is then normally stationary.However, actuation of an air clutch prevents its associated sprocketfrom spinning with chain motion and effectively locks that sprocket andclutch to the chain. Since the clutch is secured to the carriage, thecarriage will be carried along the rails by the chain in a lineardirection which is dependent upon which portion of the chain was soengaged. The carriage will move in one direction until the thenoperative clutch is de-actuated and the other clutch is actuatedwhereupon the carriage reverses direction.

Automatic actuation and de-actuation of the two air clutches is achievedwith the use of a four way, two position, pilot operated spool valvewhich is mounted on the carriage and which is provided with a suitablesource of compressed air. Two control shafts extend from either side ofthe spool valve. Each of the control shafts is arranged to eventuallycontact a respective one of two shock absorbers which are eachadjustably secured to the housing. The spool valve is arranged toactuate one clutch while simultaneously deactivating the other. When airis supplied to the spool valve it will assume one of two positions andactuate one of the two clutches. The carriage will move in a particulardirection until one of the spool valve control shafts contacts one ofthe two shock absorbers. At the moment of contact the spool valveassumes its other position deactuating the then operative air clutch andactuating the then inoperative air clutch. In this manner carriagedirection is automatically reversed and the carriage is caused toreciprocate between the two shock absorbers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a carriage reciprocator and positioneraccording to this invention; for clarity of presentation a housing towhich some of the elements are attached is not shown and certaindimensions have been exaggerated.

FIG. 2 is a partial cross-sectional view, taken along the lines 2--2, ofthe device shown in FIG. 1; this view highlights the configuration of anair clutch and associated carriage chain sprocket both of which are partof the device shown in FIG. 1.

FIG. 3 is a plan view, partially sectioned of the air clutch shown inFIG. 2 and is taken along the line 3--3 in FIG. 2.

FIG. 4 is a plan view, partially sectioned, of the carriage chainsprocket shown in FIG. 2 and is taken along the line 4--4 in FIG. 2.

FIG. 5 is a schematic diagram of the air clutches and a controllingspool valve, all of which are part of the device shown in FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, the carriage reciprocator and positioner includes aconventional variable speed motor 12 which is conventionally arranged toturn a driven sprocket 14. An idler sprocket 16, spaced apart from, butin the same plane as, the driven sprocket 14, is also provided. Acontinuous roller chain 22 extends around and between the drivensprocket 14 and the idler sprocket 16. An upper rail 18 and a lower rail20 are also provided. The rails 18, 20 have hexagonal cross sections.The rails 18, 20 lie in a plane parallel to but behind the plane inwhich the sprockets 14, 16 and chain lie.

For clarity of presentation, the housing which supports the motor 12,idler sprocket 16 and rails 18, 20 is not shown in FIG. 1. However, itis to be understood that these elements are conventionally secured tosuch unshown housing.

A carriage 24 rides on and between the upper and lower rails 18, 20.Four parallel and spaced axles 26 project rearwardly from the carriage24. The axles 26 are secured to the carriage 24 by any conventionalmeans such as bolts 30. Each axles 26 is provided with a rotatable wheel28. Two of the wheels 28 are arranged to move along the upper rail 18and the other two wheels 28 are arranged to move along the lower rail20. The carriage 24 is provided with at least one support pin 25 whichmay be secured to the carriage in any suitable fashion and upon whichany suitable element, such as a spray gun, may be supported.

Upon the carriage 24 are mounted a four way spool valve 32, twoidentical air clutches 34, 35 and two identical carriage chain sprockets36 (one of which does not appear in FIG. 1). The spool valve 32 issecured to the carriage 24 with a standoff support 33.

With further reference to FIG. 1, the spool valve 32 is provided with anair inlet 32a and air outlet 32a'. Compressed air is fed to the inlet32a from a controllable source (not shown) through a hose (not shown) ofappropriate length. Each of two air control lines 32b, 32c extends fromthe spool valve 32 to a respective one of the two air clutches 34, 35.Each of two spool valve control shafts 32d, 32e extend from a respectiveside of the spool valve 32 in a plane parallel to the plane in which thechain 22 lies.

Each of two shock absorbers 38, 39 is adjustably set opposite arespective one of the two spool valve control shafts 32d, 32e. Each ofthe two shock absorbers 38, 39 is movably mounted on a housing (notshown) with a respective one of two support bars 38a, 39a. The distancebetween the shock absorbers 38, 39 is defined as the stroke of thecarriage 24. The stroke may be made smaller or larger by adjusting thedistance between the shock absorbers 38, 39. (As will be made clearerbelow, when one of the two air clutches 34, 35 is actuated, the carriage24 will move in one direction until one of the two spool valve controlshafts 32d, 32e contacts a respective one of the two shock absorbers 38,39. At the moment of contact the spool valve 32 automaticallydeactivates the operative one of the two air clutches 34, 35 andactuates its counterpart. This action causes the carriage 24 to move inan opposite direction until the other one of the two spool valve controlshafts 32d, 32e contacts the other one of the two shock absorbers 38,39. In this manner, the carriage 24 is caused to reciprocate between thetwo shock absorbers 38, 39).

Referring to FIG. 2, which is a cross section, along the line 2--2, ofthe device shown in FIG. 1, a detailed view of one of the two identicalair clutches 34, 35 and of one of the two identical carriage chainsprockets 36, 37 is shown.

The air clutch 34 includes three major elements: a clutch cylinder 340,which is stationary with respect to the carriage 24, a clutch piston 341which is axially movable with respect to the clutch cylinder 340, and afriction liner 342 which is secured to the flat head 341a of the clutchpiston 341.

The clutch cylinder 340 is substantially circular in shape and isrigidly secured to the carriage 24 by any suitable means (not shown).The clutch cylinder 340 is provided with an air inlet 340a whichaccommodates the air control line 32b. The clutch cylinder 340 is alsoprovided with a centrally located, elongated, cylindrically shaped hub340b which is flanked by two cylindrically shaped bosses 340d, 340e. Theclutch piston 341 is also substantially circular in shape. One side,defined as the piston head 341a, faces a land 36a on the carriage chainsprocket 36; the other side is provided with two circular recesses 341b,341c which flank a circular hole 341d which is concentric with the hub340b of the clutch cylinder 340. Each of the two bosses 340d, 340e onthe cylinder 340 normally repose within a respective one of the tworecesses 341b, 341c in the piston 341. This arrangement prevents thepiston 341 from rotating with respect to the cylinder 340 but allows thepiston 341 to slide along the hub 340b of the cylinder 340.

The clutch piston also includes a disc shaped friction liner 342 whichis secured to the piston head 341a by conventional means (not shown).Two cup shaped "O"-rings 343, 344 prevent air leakage as the piston 341moves along the hub 340b.

With further reference to FIG. 2, a detailed view of one of the carriagechain sprockets 36, 37 is also shown. The sprocket 36 is conventional indesign and is arranged to normally rotate on a reduced diameter portionof the hub 340b. Two captured roller bearings 36b, 36c are provided. Athreaded bolt 40, which extends from the valve support 33 and throughthe bore 340c in the hub 340b is provided with a washer 40a and a nut40b. (See FIG. 4). The two bearings 36b, 36c repose between the washer40a and the shoulder 340f of the reduced diameter portion of the hub340b. This arrangement insures not only that the sprocket 36 freelyrotates but also that a preferred distance is maintained between theland 36a of the sprocket 36 and the friction liner 342 when nocompressed air is introduced into the inlet 340a.

FIG. 2 also shows part of the housing 11 in which all of the foregoingelements are lodged. The shock absorber support bar 39a is shownextending to a housing overhang 11a which extends the length of thehousing and upon and along which the support bar 39a and its companionsupport bar 38a slide. Each of the two shock absorber support bars 38a,39a may be removably secured to a selected portion of the overhang 11aby means of a clamp 11b and bolts 11c or in any other suitable manner.

With further reference to FIG. 2, the carriage 24 is also provided withfour identical spacers 42 which project from the carriage 24 toward thechain 22. The top two of the spacers 42 support an upper chain guiderail 44 and the bottom two of the spacers 42 support a lower chain guiderail 45. Both chain guide rails 44, 45 extend the length of the carriageand insure proper registration of the chain 22 with each of the twocarriage chain sprockets 36, 37.

In FIG. 5, a pneumatic diagram of the spool valve 32 and the clutches34, 35 is presented. With the spool valve in the first position shown inFIG. 5, the lower clutch 34 is connected to a source, S, of compressedair and the upper clutch 35 is connected to the air return R. Hence thelower clutch 34 is actuated and the upper clutch 35 is deactuated.

The spool valve 32 is a four way, pilot operated, two position device ofconventional design. As is well known the spool valve 32 operates on apressure differential principal. Actuation of, for example, the controlshaft 32d exhausts its associated pilot operator to atmosphere tothereby create a pressure differential within a poppet chamber (notshown) which causes the poppets (not shown) to shift. The spool valve 32then assumes its second position and the poppets are locked until theother control shaft 32e is actuated. When the spool valve 32 assumes thesecond position, the upper clutch 35 is connected to the source, S, andthe lower clutch 34 is connected to the return, R.

OPERATION

When the variable speed motor 12 is energized, the chain runscontinuously in a clockwise direction at the speed set by the motorspeed controllers (not shown). The carriage 24 is initially stationary.When compressed air, at 75 psi for example, is introduced into the inlet32a of the spool valve 32, one of the two air clutches 34, 35 isactuated depending upon the initial condition of the spool valve 32. Ifthe lower air clutch 34 is actuated, its piston 341 will slide along itshub 340b until the friction liner 342 engages the land 36a on thecarriage chain sprocket 36. Before the liner 342 makes contact, thesprocket 36 idly spins with the motion of the chain 22. However, oncethe liner 342 fully abuts the sprocket land 36a, the sprocket 36 is nolonger free to turn. Hence the sprocket 36, chain 22, and clutch 34 areeffectively locked together. Since the clutch 34 is secured to thecarriage 24, the carriage will move linearly in chain direction "A".(See FIG. 1) The carriage will move in direction "A" until the spoolvalve control shaft 32d encounters the left shock absorber 38 at whichtime the lower clutch 34 is deactuated and the upper clutch 35 isactuated. When pressurized air is supplied to the upper clutch 34, itlocks or brakes its associated carriage sprocket 37 in the same mannerand the carriage 24 then travels linearly in direction "B" until theright spool valve control shaft 32e encounters the right shock absorber39. When contact is made, the direction of the carriage 24 is reversedand so on. In this manner the carriage 24 is caused to reciprocate untilpressurized air is no longer supplied to the spool valve 32.

It is clear that both air clutches 34, 35 act as a brake. A uniquedesign feature of the air clutch 34 is the absence of any biasingelement which would act to return the clutch piston 341 to the unengagedposition (shown in FIG. 2) when pressurized air is no longer supplied tothe clutch 34. Through experimentation it was discovered that whenpressurized air is removed from the clutch 34, the rotational movementof the freed sprocket 36, among other supposed things, creates enoughforce against the liner 342 and piston 341 to push these united elementsaway from the land 36a on the sprocket 36 so that they assume theunengaged position portrayed in FIG. 2.

I claim:
 1. A carriage reciprocator comprising:a housing; a carriagemovably mounted on said housing; a chain movably mounted on said housingand arranged to continuously present a first chain portion, moving in afirst direction, to a first portion of said carriage and to present asecond chain portion, moving in a second direction, to a second portionof said carriage; means, secured to the housing, for moving said chain;a first chain sprocket rotatably mounted on said carriage, and arrangedto operatively engage said first chain portion and arranged to normallyidly spin with chain motion; a second chain sprocket rotatably mountedon said carriage, and arranged to operatively engage said second chainportion and arranged to normally idly spin with chain motion; a firstair brake secured to said carriage and arranged to permit the spinningof said first chain sprocket when in a first state and to prevent thespinning of said first chain sprocket when in a second state; a secondair brake secured to said carriage and arranged to permit the spinningof said second chain sprocket when in a first state and to prevent thespinning of said second chain sprocket when in a second state; an aircontrol valve secured to said carriage, operatively connected to saidfirst and second air brakes, and arranged to shift between first andsecond control states wherein said first air brake is in its first stateand said second air brake is in its second state when said air controlvalve is in said first control state and wherein said first air brake isin its second state and said second air brake is in its first state whensaid air control valve is in said second control state; and meansmovably mounted on said housing for shifting said air control valvebetween said first and second control states.
 2. A carriage reciprocatoraccording to claim 1 further including:a source of pressurized air, andmeans to deliver said air to said air control valve.
 3. A carriagereciprocator according to claim 1 wherein said first and second brakeseach comprise:a cylinder secured to said carriage; a piston mounted onsaid cylinder for axial motion with respect to said piston; and afriction liner secured to said piston.
 4. A carriage reciprocatoraccording to claim 3 wherein said means for alternately moving saidfirst and second brakes into opposite first and second positionscomprises:a four-way, two position spool valve.